The present invention relates generally to a process and apparatus for sterilizing a desired material; and more particularly to such a process and apparatus which utilizes ultraviolet radiation to achieve a desired degree of sterilization.
It is well known that ultraviolet radiation (UV) in the UVC band (100 to 290 nm wavelength can be used to kill bacteria and other biological contaminants present on surfaces, in liquids, or in gases. A certain minimum amount of radiant energy is required to kill a given population of contaminants, this minimum amount depending on several factors including the concentration of contaminants on or in the material to be sterilized.
Various appliances are available which generate UV radiation to sterilize surfaces or liquids. These include air purifiers, water purifiers, medical instrument sterilizers, and other devices. Some of these devices are of the flow-through type, in which a stream of liquid or gas passes through the device, and while inside, is exposed to UV radiation. Examples of hand held sterilization appliances are disclosed in U.S. Pat. No. 4,896,042 and U.S. Pat. No. 5,900,212.
When using a UV sterilization appliance, there is often no reliable way to determine whether the amount of UV energy being emitted by the appliance is sufficient for sterilization. Many different faults may occur in such appliances which could diminish the amount of energy output sufficiently to prevent complete sterilization. Such faults may include old or defective UV sources, defective drive circuits, inadequate power supplies, or low ambient temperatures.
Thus, it is an object of the present invention to provide a method and apparatus for accurately determining whether a material has received an adequate amount of UV exposure to achieve proper sterilization. It is a further object of the present invention to provide such a method and apparatus which is facile and cost effective to use. Still further, it is an object of the present invention to provide such a method and apparatus having a sterilization monitoring means which may be disposable and/or reusable.
The present invention addresses and solves the above-mentioned problems and meets the enumerated objects and advantages, as well as others not enumerated, by providing an apparatus for sterilizing a desired material, the apparatus comprising an ultraviolet (UV) radiation generator for generating ultraviolet radiation in the UVC range, wherein the generator is adapted to direct the ultraviolet radiation at the desired material. The apparatus further comprises means for monitoring the desired material to detect an amount of cumulative exposure thereto by the ultraviolet radiation in the UVC range. The monitoring means may comprise an indicator strip adapted to be positioned adjacent at least one of the desired material and the generator. The indicator strip may have a photochromic material disposed thereon, wherein the photochromic material changes in appearance in proportion to intensity and duration of exposure to the ultraviolet radiation in the UVC range.
A method for sterilizing an aqueous solution according to the present invention comprises the steps of: directing ultraviolet radiation (UV) in the range from about 200 nm to about 290 nm toward the aqueous solution; and monitoring the aqueous solution to detect an amount of cumulative exposure thereto by the ultraviolet radiation. The monitoring step may be performed by an indicator strip as described above.